Storage tube target and method for making same



United States Patent 9 Claims. (a. 313-68) The present invention relatesto a process for manufacturing storage tube targets and to the targetsproduced thereby. More particularly, it relates to a process formanufacturing targets having induced conductivity is characterized bypreliminarily activating an insulating material with an activatingmetal. The present invention also concerns targets of inducedconductivity having a porous insulating layer exhibiting inducedconductivity properties and a remanence that may be accuratelypredetermined.

Known in connection with storage tubes are the socalled inducedconductivity targets, that is, targets comprising a metallic layer incontact with an insulating layer made of a dielectric material, such aszinc sulfide, having the property of becoming momentarily conductivewhen electrons quickly traverse the insulating layer, by liberatingalong the paths thereof a large quantity of secondary electrons.

It is also known that if the electrons which bombard the target carry asignal, this signal is inscribed in the form of a voltage relief on theinsulating face of the target. The length of time of subsistence of therelief in this presence of read-out is called the remanence of thetarget. This remanence conserves a certain minimum value even if oneproceeds to erase or rub out the potential relief by depositing positivecharges on the insulating face of the target.

A process for the manufacture of these targets has already beendescribed in the Us. Patent No. 2,998,331 to R. Rigot et al:, assignedto the assignee of the present application, in which an insulation withinduced conductivity was vaporized on a film of collodion containing acertain amount of activating impurities which became lodged, after thedestruction of the collodion, within the surface of the insulatinglayers of slightly below its surface.

Experience and tests indicate that the targets manufactured inaccordance with this prior art process possess a minimum remanence,during the erasing or rubbing out procedure, in excess to the valuesdesired, and that. These targets did not lend themselves to theestablishment of a predetermined remanence of subsistence of the reliefwithin a desirable range, but could only be manufactured with a singleremanence value, within very narrow manufacturing deviations.

The present invention is directed to a manufacturing process whichproduces a target substantially free from these shortcomings, that is, atarget which has a substantially reduced minimum remanence duringerasure, and which may be manufactured with a predetermined value forthe remanence of subsistence of the relief and which can be selectedfrom a large range of desirable remanences.

Accordingly, it is an object of the present invention to provide aprocess for the manufacture of induced conductivity targets for storagetubes which eliminates the shortcomings and drawbacks encountered in theprior art.

Another object of the present invention resides in a process for themanufacture of induced conductivity targets for storage tubes whereinthe various steps may "ice be so chosen and controlled as to provide asuitable selection from a substantial number of different remanences.

Still a further object of the present invention resides in a process forthe manufacture of induced conductivity targets which readily lendsitself to the manufacture of targets having a predetermined remanencewhich may be readily controlled and maintained within desired limits.

Another object of the present invention resides in a method forproducing induced conductivity targets for storage tubes which possess aminimum remanence, during erasure, which is compatible with valuesdesired in practice.

A further object of the present invention resides in an improved targetwith induced conductivity for storage tubes having remanencecharacteristics which are very satisfactory for practical applications.

Still another object of the present invention resides in a target withinduced conductivity wherein the remanence may be predetermined and isof such a value that it is suitable for practical use.

These and other objects, features and advantages of the presentinvention will become more obvious from the following description of theprocess in accordance with the present invention, and the targetresulting therefrom.

The process according to the present invention comprises utilizing theinsulating material having the property of induced conductivity andactivated, in that state by an activating metal, such as manganese,copper or analogous material, this metal being present in an amount of0.1 to 10% by weight, depending on the desired value of the remanence.This activated substance is then deposited on the metallic layer, forexample, aluminum or on a film of collodion which is utilized as atemporary support between the metallic layer and the insulating layer.The activated substance is deposited on the metallic layer byvaporization under vacuum using conditions such that the depositedinsulating layer is porous.

It will be readily understood that the porosity of the insulating layerproduces the desired efiect on the minimum remanence during erasure.Since the capacity of a porous structure is reduced with respect to thatof a dense structure of the same materials and dimensions in such amanner that the time constant of discharge is reduced, the erasurerequires less time. However, if this porous structure were made of adielectric material such as pure Zinc sulfide, its remanence ofsubsistence of the relief would also be very slight with respect to adense structure, and would find itself outside of the range of desirableremanences. The addition of an activator such as Mn or Cu or ananalogous material to the primary material intended to be vaporizedunder vacuum permits the restablishment of this remanence and brings thesame back within the limits of the desirable range. Furthermore, sincethe value of the remanence within this range is a function of the dosageof the activator, by a suitable choice of the dosage it is possible tomanufacture a target with predetermined remanence.

As an illustrative example, zinc sulfide is activated with manganese inan amount of about 0.1% to 10% by weight, to obtain a target in whichthe remanence of subsistence of the relief is equal to 2 to 20 times thetime required by the signal to attain one-half of its initial value,depending on the amount of activator used. The activated zinc sulfide isthen vaporized, for example, on a film of aluminum or collodion underthe conditions well known to one skilled in the art to obtain a porousdeposit. Well known process conditions include, for example, a vacuum ofabout 10" mm. Hg. and a relatively low temperature of about 950 C. Theminimum remanence during the erasure of this target is less than twoseconds. For purposes of comparison it should be noted that the targetsmanufactured by the process of the aforementioned prior art patents havea minimum remanence during erasure of not less than 8 seconds, and theremanence of subsistence of the relief was always fixed, except fordeviations in manufacture, to the same value, for example in tens ofseconds, and was not controllable or adjustable.

While we have described one embodiment in accordance with the presentinvention, it is understood that the same is not limited thereto but issusceptible to numerous changes and modifications within the spirit andscope thereof, as known to a person skilled in the art, and we thereforedo not wish to be limited to the details shown and described herein butintend to cover all such changesand modifications as are encompassed bythe scope of the appended claims.

We claim:

1. A method for controlling, during manufacture, the remanence time of astorage tube target having a porous insulating layer providing inducedconductivity properties, compirsing the steps of:

selecting a predetermined amount of activating metal selected from thegroup consisting of manganese and copper and adding the same to theinsulating layer prior to forming said layer.

2. A method for controlling, during manufacture, the remanence time of astorage tube target having a porous insulating layer providing inducedconductivity properties, comprising the steps of:

selecting by weight of about a predetermined amount of activating metalselected from the group consisting of manganese and copper and addingsame to the insulating layer prior to forming said layer.

3. A storage tube target having a predetermined remanence comprising athin aluminum layer support and a porous insulating layer deposited onsaid thin aluminum layer support, said insulating layer having inducedconductivity properties and consisting essentially of a zinc sulfideinsulating material mixed with about 0.1 to 10% by weight of anactivating metal selected from the group consisting of manganese andcopper, said activating metal having activating properties for the zincsulfide.

4. A process for producing storage tube targets which comprises coatingone surface of an aluminum layer with an insulating layer having inducedconductivity properties and consisting essentially of a zinc sulfideinsulating material mixed with about 0.1 to 10% by weight of anactivating metal having activating properties for said insulatingmaterial, said activating metal selected from the group consisting ofmanganese and copper, and vaporizing said insulating layer in a vacuumand at a temperature sufiicient to produce a porous insulating layer.

5. The process of claim 4, wherein a film of collodion is utilized as atemporary support between the metallic layer and the insulating layer.

6. The process of claim 4, wherein the vacuum is about 10- mm. Hg andthe temperature is about 950 C.

7. A process for producing storage tube targets which comprises coatingone surface of an aluminum layer with an insulating layer having inducedconductivity porperties and consisting essentially of a Zinc sulfideinsulating material mixed with about 0.1 to 10% by Weight of anactivating metal having activating properties for said insulatingmaterial, said activating metal selected from the group consisting ofmanganese and copper, and vaporizing said insulating layer in a vacuumof about 10- mm. Hg and at a temperature of about 950 C.

8. A process for producing storage tube targets which comprises coatingone surface of a film of collodion with a metallic layer of aluminum,coating the other surface of said film with an insulating layer havinginduced conductivity properties and consisting essentially of a zincsulfide insulating material mixed with about 0.1 to 10% by weight of anactivating metal having activating properties for said insulatingmaterial, said activating metal selected from the group consisting ofmanganese and copper, vaporizing. said insulating layer in a vacuum at atemperature sufiicient to produce. a porous insulating layer, and bakingsaid coated film at a temperature sulficient to eliminate said collodionfilm, whereby said insulating layer directly coats said metallic layer.

9. The process of claim 8, wherein the vacuum is about 10- mm. Hg andthe vaporizing temperature is about 950 C.

References Cited UNITED STATES PATENTS 8/1962 Nicholson 117-211 9/1965Hannam 31389

1. A METHOD FOR CONTROLLING, DURING MANUFACTURE, THE REMANENCE TIME OF ASTORAGE TUBE TARGET HAVING A POROUS INSULATING LAYER PROVIDING INDUCEDCONDUCTIVITY PROPERTIES, COMPRISING THE STEPS OF: SELECTING APREDETERMINED AMOUNT OF ACTIVATING METAL SELECTED FROM THE GROUPCONSISTING OF MANGANESE AND COPPER AND ADDING THE SAME TO THE INSULATINGLAYER PRIOR TO FORMING SAID LAYER.